Gasoline fuel

ABSTRACT

Total combustion and evaporative emissions from gasoline pump fuels can be controlled with total emissions no higher than those currently allowed by the addition of an evaporative factor such as RVP to the model predicting emissions, based on a number of considerations including the sensitivity of emission parameters (toxics, hydrocarbons, CO and NOx) as related to the variables in the predictive model (oxygenate content, sulfur, T 90 , T 50 , aromatics, olefins, benzene and RVP). The present pump gasolines will normally have compositions including T 10  no greater than 140° F., T 90  no greater than 330° F., RVP no greater than 7 psi and usually lower and sulfur no greater than 50 ppmw. Oxygenates may be eliminated, permitting T 50  values to increase which is not unfavorable from the viewpoint of total emissions provided other parameters are held within specified limits. Aromatics, olefins and benzene are normally held to maximum of 35, 10 and 1 vol % respectively to achieve satisfactorily low total emissions.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. Ser. No. 09/226,409filed Jan. 6, 1999 now abandoned which claims priority of U.S. Ser. No.60/070,814 filed Jan. 8, 1998.

FIELD OF THE INVENTION

The present invention relates to fuels and particularly to gasolinefuels suitable for use in road vehicles. It is more particularlydirected to gasoline fuels suitable for use in road vehicles as astandard pump fuel suitable to be supplied throughout the manufacturingand distribution system of the petroleum refining industry in largequantities.

BACKGROUND OF THE INVENTION

One of the major environmental problems confronting certain areasincluding major cities, in the United States and other countries is ofatmospheric pollution associated with the emission of gaseous pollutantsfrom automobiles, including both evaporative emissions and exhaust gaspollutants. This problem may be acute in major metropolitan areas suchas Los Angeles, Calif. where atmospheric conditions in combination withlarge numbers of automobiles create appropriate conditions foraggravated air pollution.

In addition to evaporative emissions from the gasoline tanks of thevehicles and emissions from product terminals and tankers, hydrocarbonsare also found as unburned or incompletely burned hydrocarbons in theexhaust emissions together with nitrogen oxides (NOx) and carbonmonoxide (CO), all of which contribute to air pollution.

The composition of motor gasolines commercially sold for normal roadvehicle use in certain areas of the United States is now restricted byFederal and, in some cases, by State regulations. The California AirResources Board (CARB) has established a legal reference framework forthe sale of motor gasolines in California which is intended to reducethe severity and extent of air pollution in that State from gasolinepowered road vehicles and other mobile sources fueled with motorgasoline. The CARB regulations for Clean Burning Gasolines (CBG) arefound in Title 13 of the California Code of Regulations, principally inSections 2260 et seq., with Sections 2260 to 2270 dealing with thepredictive model (PM) established under the regulations. Reference ismade to these regulations as well as to the document “CaliforniaProcedures for Evaluating Alternative Specifications for Phase IIReference Gasolines Using the California Predictive Model”, for detailsof the model and the test procedures to be used in conjunction with it.The present invention deals mainly with gasolines which either conformto the California regulations or which provide emissions no higher thanthose permitted under the current regulations. The US federalregulations are set by the Environmental Protection Administration (EPA)which has established initially a simple predictive model (the SimpleModel) and, subsequently, a Complex Predictive Model (the Complex Model)for predicting vehicle evaporative and exhaust emissions.

The CARB Regulations regulate the composition of road vehicle motorgasolines in two ways. A simple prescriptive compositional standard forCBG may be followed but as an alternative, a fuel may be evaluated bythe predictive model with the requirement that exhaust emissions shouldbe no higher than those resulting from a fuel which conforms to thecompositional specifications. The predictive model ultimately setslimits on vehicle emissions according to various compositionalparameters, for example, sulfur, olefins and aromatics contents as wellas by reference to distillation characteristics including thedistillation points including the 10%, 50% and 90% distillation points(T₁₀, T₅₀, T₉₀) of the gasoline. The “D-86 Distillation Point” refers tothe distillation point obtained by the procedure identified as ASTM D86-82, which can be found in the 1990 Annual Book of ASTM Standards,Section 5, Petroleum Products, Lubricants, and Fossil Fuels. Unlike theEPA model, the CARB predictive model has no specification forevaporative emissions, as commonly measured by the Reid Vapor Pressure(RVP) method, confining itself to exhaust emissions produced on thecombustion of the gasoline fuels. “Reid Vapor Pressure” (RVP) is apressure determined by a conventional analytical method for determiningthe vapor pressure of petroleum products. In essence, a liquid petroleumsample is introduced into a chamber, then immersed in a bath at 100° F.(37.8° C.) until a contstant pressure is observed. Thus, the RVP is thedifference, or the partial pressure, produced by the sample at 100° F.(37.8° C.). The complete test procedure is reported as ASTM test methodD-323-89 in the 1990 Annual Book of ASTM Standards, Section 5, PetroleumProducts, Lubricants, and Fossil Fuels. The EPA Complex Model provides apredictive model for evaporative effects of various compositions and itappears that consideration of evaporative emissions is a relevant factorsince a review of recent CARB emission inventories indicates thatevaporative emissions contribute about 30% to total hydrocarbonemissions.

CBG specifications set by CARB set absolute limits on certain gasolineparameters such as sulfur content and, in addition, permit thecompositions of pump gasolines to be varied within these absolute limitseither by composition on a per gallon or an averaged basis or byreference to the Predictive Model. The compositional specifications areas shown in Table 1 which follows:

TABLE 1 CBG Gasoline Specifications Property Caps Per Gallon AverageSulfur, ppm 80 40 30 Benzene, wt % 1.2 1.0 0.8 Aromatics, vol % 30 25 22Olefins, vol % 10 6 4 Oxygen, wt % 2.7 1.8/2.2 RVP, psi 7.0 7.0 T₅₀, °F. 220 210 200 T₉₀, ° F. 330 300 290

The oxygenate content, set at a maximum of 2.7 wt % in Table 1 above (asoxygen, corresponding to about 10 wt % or more, e.g., 12 wt % as actualoxygenate), may be increased to 3.5 percent under a proposal beingconsidered by CARB. See Notice of Continuation of Public Hearing toConsider an Amendment to the California cleaner Burning GasolineRegulations by Increasing the Cap Limit for Oxygen from 2.7 to 3.5Percent by Weight, Hearing set for 10 Dec. 1998, Sacramento, Calif. Theoxygenate content may be varied under the predictive model as long asthe fuel results in emmissions no worse than those resulting from theaverage/per gallon fuel selected as the basis for comparison. Thefederal RFG oxygenate requirement has to be observed year round in theCalifornia areas covered by federal RFG (Los Angeles, Sacramento and SanDiego) and in addition, a minimum 1.8 wt. pct. oxygen is required incertain areas in California during the winter for CO control (LosAngeles Metro area, Imperial County and for the next two years onlyFresno and Lake Tahoe).

Proposals have been made in the past for the development of motorgasolines which produce lower amounts of gaseous pollutants oncombustion, notably U.S. Pat. Nos. 5,288,393; 5,593,567; 5,653,866 and5,837,126, Jessup et al., assigned to Union Oil Company of California.According to the Jessup patents, the principal factor influencing thehydrocarbon and/or CO exhaust emissions is the 50% distillation point(T₅₀) which is held at a maximum value of 215° F. (102° C.) with thehydrocarbon and CO emissions progressively decreasing as T₅₀ is reducedbelow this value. It is stated that preferred fuels have T₅₀ of 205° F.(96° C. or less) with best results being attained with T_(═)being below195° F. (91° C.) NOx emissions are stated to be minimized or reduced independence upon RVP as the principal factor with T₁₀ as a secondaryfactor. NOx emissions are stated to decrease as RVP is decreased to 8.0psi (0.54 atm) or less, preferably to 7.5 psi (0.51 atm) or less with anexpressed preference for values below 7.0 psi (0.48 atm). The 10%distillation point and the olefin content are stated to be of secondaryimportance with respect to NOx emissions with olefin contents below 15vol % providing some reduction in NOx emissions, preferably with zerocontent of olefins. The 10% point (T₁₀) is stated to provide somereduction in NOx emissions at values below 140° F. (60° C.). Althoughdecreases in olefin content are likely to be more acceptable to therefiner than decreasing T₁₀, it is stated that the olefin content willbe the secondary variable providing the most flexibility to the refinerin altering gasoline composition to reduce NOx emissions. The conclusionis expressed that best results are attained when both the olefin contentis below 15 vol %, preferably 0, and the RVP is no greater than 7.5 psi(0.51 atm) with the T₁₀ preferably being below 140° F. (60° C.). Anumber of gasoline compositions are set out in the Jessup patentstogether with calculated and experimental emission data for such fuels.

While the predictive models utilized by the EPA and CARB provide acomprehensive framework for evaluating the potential effects ofvariations in motor gasoline composition, further development work hasshown that it is possible to control emissions effectively—and even toreduce emissions—below current levels while giving the refineradditional flexibility in the compositions of the gasoline's. This isbased on a number of considerations including the sensitivity ofemission parameters (toxics, hydrocarbons, CO and NOx) as related to thevariables in the CARB predictive model (oxygenate content, sulfur, T₉₀,T₅₀, aromatics, olefins, benzene and RVP). Toxics and total hydrocarbone(THC's) in the CARB predictive model are very sensitive to T₅₀ valuesabove 210° F. but these increases can be offset by adjusting othervariables including an evaporative factor such as RVP, as well asdecreased sulfur. If appropriate adjustments in the compositinalparameters are made it may possibly permit increased olefins levels atthe same time, which is a useful consideration for refiners whichutilize a significant amount of FCC gasoline in the final blend. Whilecertain compositional variations may fall within existing regulatorylimits, certain others fall outside current limits but again, have thepotential of providing lower total emissions than those resulting fromcompositions which are in accordance with current limits. The potentialfor providing lower total emissions (evaporative and exhaust) indicatesthat by including an evaporative parameter to the predictive model itmay be possible when offsets from other properties are factored in, toprovide reductions in hydrocarbon emissions sufficient to offset theincreases resulting from an increase in T₅₀. Further, the addition of anevaporative parameter to gasoline compositions may be prudent in view ofthe finding that evaporative emissions approximate to some 32% of totalhydrocarbon emissions with projections showing an increase after theyear 2000. Reductions in the RVP would provide improved flexibility inmanufacturing and blending operations for pump gasoline withoutenvironmental harm. In fact, the benefits from including an evaporativeparameter in the CARB model could be significant. Each 0.1 psi reductionin RVP provides hydrocarbon emission reductions equivalent to areduction of 2° F. (1° C.) in T₅₀.

The effects of including an evaporative parameter in the fuelcertification model and reducing RVP from 7.0 to 6.6 psi in thepredictive model were investigated with respect to the CARB predictivemodel by systematically varying fuel properties within the followingranges: T₅₀ 210-220° F., T₉₀ 295-330° F., sulfur 5-35 ppm, aromatics12-28 vol %, and olefins 2-10 vol %. Oxygen was held at 2% and benzeneat 0.7%. The percent of fuels tested which meet all CARB emissioncontraints are summarized in Table 2 below:

TABLE 2 T₅₀, Base RVP Added RVP Added ° F. Model Exhaust and EvaporativeEvaporative Only 210 48% 81% 63% 212 40% 77% 61% 214 31% 71% 57% 216 21%64% 52% 218 13% 52% 44% 220  5% 38% 34%

The evaporative parameter here is based on the CARB revised draft“Outline of an Evaporative Modeling Proposal”, revised 6 May 1998,original distributed for public consultation 5 Feb. 1998.

From these results it is clear that the addition of an evaporativefactor which can account for the beneficial effect of reducing RVP hasthe potential for improving actual emission levels. In the base model itis difficult to increase T₅₀ beyond 214° F. unless sulfur and aromaticsare very low. With the RVP factor added, however, there is a significantincrease in flexibility and T₅₀ levels of 220° F. and higher arepossible. The use of T₅₀ values above 215° F. therefore becomespossible, with values in the range of 215° F. to 220° F. representing anarea in which there is significant potential for the formulation ofgasolines with acceptable levels of total emissions according to thestandards now prevailing in California. The greatest flexibility isprovided when the exhaust RVP effects are also added due to the addedNOx benefits.

SUMMARY OF THE INVENTION

According to the present invention, pump gasolines are formulated tohave total emissions (evaporative plus combustive) no higher than thosewhich would be permissible under current regulations, specifically theCARB regulations referred to above. Although variation in the currentregulations may be required in certain instances, it is believed thatactual emissions (total) would be at least equivalent that is,equivalent or better, to those resulting from current fuels. The presentgasolines are, of course, lead-free in accordance with current EPAregulations.

Conceptually, the present fuels can be categorized in three ways. Thefirst group of fuels is characterized by a T₅₀ in the range of 210 to215° F. and with other compositional properties including low sulfurlevels which confer good emission performance. The second group has aneven higher T₅₀, in the range of 215 to 220° F. and again with othercompositional characteristics which confer good emissions performance.The third group has a low T₅₀ value below about 210° F. but here, it hasbeen found that it is possible to enlarge the volume of the gasolinepool by the use of an extended T₉₀ about 315° F., normally from 315° F.to 330° F.

The present gasoline fuel compositions may by produced by conventionalrefining and blending techniques using such refinery processes asdistillation, cracking, reforming and alkylation with blending of theappropriate fractions such as naphtha, FCC gasoline, reformate andalkylate.

DESCRIPTION OF THE FIGURES

FIG. 1 presents the percentage change in emissions in response to T₅₀ (°F.), all other fuel properties being held constant.

FIG. 2 presents the percentage change in emissions in response to oxygencontent, all other fuel properties being held constant.

FIG. 3 presents the percentage change in emissions in response to olefincontent, all other fuels properties being held constant.

DETAILED DESCRIPTION

In the present gasoline boiling range pump fuels, the followingparameters in Table 3 will normally be followed for the compositionswhich utilize T₅₀ values in the range of 210 to 220° F.:

TABLE 3 Limits Parameter Broad Intermediate Narrow T₁₀, ° F. <=140 <=135<=130 T₅₀, ° F. >210 211-215/215-220 211-213/215-218 T₉₀, ° F. <330305-320 310-315 E₂₀₀, ° F. <=46 40-45 41-44 E₃₀₀, ° F. <=90 82-89 84-88RVP, psi <=7.0 6.6-6.9 6.7-6.85 S, ppmw <=50 10-25 (SUL) 10-20 (SUL)Oxygen, wt % <=3.5 1.5-2.9 1.8-2.2 Aromatics, vol % <=35 10-28 10-20Olefins, vol % <=10 1-6 1-5 Benzene, vol % <=1.0 <=0.80 (SUL) <=0.70(SUL) Paraffins, vol % <=75 <70 <65 API° >=59 60-62 (SUL) 60-62 (SUL)Note: SUL = Super Unleaded, (R + M)/2 >= 92 RUL = Regular Unleaded, (R +M)/2 = 87-90 E₂₀₀ is the percent by volume of fuel boiling ≦ 200° F.E₃₀₀ is the percent by volume of fuel boiling ≦ 300° F.

Examples of super unleaded (R+M)/2=92 and regular unleaded (R+M)=87,conforming to these parameters and providing emissions levels no greaterthan those allowable under current CARB requirements would be asfollows:

TABLE 4 GASOLINE FUELS—SUPER UNLEADED GRADE SUL S, Oxy, No. APIAromatics Benzene E₂₀₀ E₃₀₀ Olefins RVP ppm wt % T₅₀ T₉₀ 1 61.40 13.30.3 43.4 85.8 0.9 6.89 15 2.4 211 320 2 59.00 24.2 0.92 43.9 87.3 4.76.78 9 1.8 211 311 3 61.20 16.9 0.65 42.9 88.5 5.1 6.95 10 1.9 211 307 459.00 21 0.82 43.8 87.3 3.8 6.96 13 1.8 211 311 5 59.10 21.9 0.81 43.987.4 2.9 6.77 17 1.9 211 310 6 58.80 24.7 0.81 44 87.3 3.7 6.64 18 1.9211 311 7 60.10 22.2 0.8 43.8 88.1 3.3 6.83 19 1.8 211 308 8 59.00 25.70.74 42.8 87.2 4.4 6.79 9 2 212 311 9 59.70 23.1 0.7 42 87 3 6.83 15 1.9213 311 10 61.00 18.1 0.3 41.2 87.1 1.4 6.83 11 2.5 214 314

TABLE 5 GASOLINE FUELS—REGULAR UNLEADED GRADE RUL S, Oxy, No. APIAromatics Benzene E₂₀₀ E₃₀₀ Olefins RVP ppm wt % T₅₀ T₉₀ 1 59.70 11.60.3 44.1 84.6 5.1 6.69 27 2.4 213 320 2 58.70 16 0.3 44.6 83.2 2.5 6.9825 2.6 213 325 3 59.30 17.4 0.4 43.9 ? 2.2 6.91 22 2.1 213 315 4 58.7014.2 0.3 43.3 84.3 5.4 6.6 24 2.3 215 321 5 57.80 18.2 0.5 44.6 85.6 4.46.85 16 2.2 212 315 6 57.60 20.4 0.6 44.4 85.6 4.1 6.61 17 2.2 212 312 757.90 22.3 0.7 44.1 87.2 5 6.82 15 2 212 307 8 57.60 19.2 0.6 45 85 6.76.66 19 2.1 211 316

The gasolines set out above demonstrate that with RVP below 7.0 psi andsulfur below 50 ppmw, desirably below 30 ppmw, e.g., 25, 20, 15 ppmw oreven lower, with oxygenate contents varying up to the permitted CARB capof 2.7 wt %, conforming pump gasolines may be blended.

The term pump gasoline is used here to refer to gasolines which are tobe sold in commerce for automotive uses from the normal industrydistribution system after manufacture in quantity by normalmanufacturing and blending operations. This will normally imply that ona given day, and usually on a daily basis over a period of at least onemonth, at least 1,000 and more preferably at least 10,000 automobileswill be provided with a “pump gasoline” of the type described here. Thepresent pump gasolines are especially useful in highly congested areas,e.g., within the limits of a city or county encompassing a population of500,000 or more people.

The effect of appropriate control of compositional parameters may beshown by the following comparisons. A number of low RVP gasolines arecompared for emissions with a gasoline conforming to the flat limits ofT₅₀ 210° F., T₉₀ 300° F., sulfur 40 ppmw, aromatics 25 vol %, andolefins 6 vol %. Oxygen was held at 1.8-2.2% and benzene at 1%, RVPmeets the 7 psi limit.

TABLE 6 RELATIVE POLLUTANT LEVELS Fuel No. 1 2 3 4 5 6 7 8 9 10 RVP 6.896.78 6.95 6.96 6.77 6.64 6.69 6.98 6.91 6.6 T₅₀ 211 211 211 211 211 211213 213 213 215 T₉₀ 320 311 307 311 310 311 320 325 315 321 Aromatics13.3 24.2 16.9 21 21.9 24.7 11.6 16 17.4 14.2 Olefins 0.9 4.7 5.1 3.82.9 3.7 5.1 2.5 2.2 5.4 Oxygen 2.4 1.8 1.9 1.8 1.9 1.9 2.4 2.6 2.1 2.3Sulfur 15 9 10 13 17 18 27 25 22 24 Benzene 0.3 0.92 0.65 0.82 0.81 0.810.3 0.3 0.4 0.3 Relative Pollutant Levels NOx −4.33301 −1.98592 −2.48582−2.65 −2.83914 −2.13134 −2.07 −2.75908 −3.5995 −1.98735 VOC −2.4844−0.40846 −2.84479 −0.68 −0.11216 0.513447 −2.41 1.065478 0.426402−0.04762 Toxics −18.5283 −2.95228 −11.1558 −7.45 −8.03918 −4.75931−12.85 −13.327 −14.5965 −10.9451 Fuel No. 11 12 13 14 15 16 17 18 RVP6.85 6.61 6.83 6.83 6.82 6.66 6.83 6.79 T₅₀ 212 212 213 214 212 211 211212 T₉₀ 315 312 311 314 307 316 308 311 Aromatics 18.2 20.4 23.1 18.122.3 19.2 22.2 25.7 Olefins 4.4 4.1 3 1.4 5 6.7 3.3 4.4 Oxygen 2.2 2.21.9 2.5 2 2.1 1.8 2 Sulfur 16 17 15 11 15 19 19 9 Benzene 0.5 0.6 0.70.3 0.7 0.6 0.8 0.74 Relative Pollutant Levels NOx −2.64111 −2.46482−2.75153 −3.56778 −1.7807 −1.33299 −2.50787 −1.96937 VOC −0.56947−0.04891 1.027375 −0.12701 −0.45248 −0.69121 −0.20234 0.326799 Toxics−10.8406 −9.39936 −7.91296 −16.3274 −6.92238 −5.97076 −7.71766 −4.31875

Table 6 above shows that not all gasolines may be conforming sincereduction of all pollutants is required and Fuels No. 6, 8, 9, 13, 18have elevations in one of the pollutant levels. All gasolines have,however, T₅₀ values above 210° F., indicating that it is possible toachieve conformance with regulatory standards without maintaining T₅₀below that value.

That the use of T₅₀ values above 210° F. for reducing emissions belowregulatory limits is not indispensable is shown by the following data.Further examples of reduced pollution gasolines (SUL) are set out belowin Table 7, the first three being in conformity with the existing CARBCBG requirements while the second three do not conform to existingrequirements but nevertheless are comparable in terms of total pollutantemissions when evaporative emissions are accounted for.

TABLE 7 Oxy - Oxy - Ben- RVP T₅₀ T₉₀ Aromatics Olefins min max Sulfurzene psi ° F. ° F. vol % vol % wt % wt % ppmw vol % CBG fuels withexisting model 7 214 300 22 4 1.8 2.2 15 0.8 7 212 310 22 4 1.8 2.2 150.8 7 200 325 20 10 1.8 2.2 10 0.7 CBG fuels with modified model 6.6 220310 20 4 1.8 2.2 10 0.7 6.6 218 310 24 4 1.8 2.2 15 0.7 6.6 214 320 24 41.8 2.2 20 0.7

The acceptability of higher T₅₀ values when the evaporative factor isadded is further shown by Table 8 following setting out the compositionsof pump gasolines with total emissions levels no higher than thosepermitted by current California standards when evaporative emissions areaccounted for.

TABLE 8 T₅₀ Aroms., T₉₀ Sulfur Olefins Oxygen, Benzene RVP ° F. vol % °F. ppm vol % wt % vol % psi No. Max. Max. Min. Max. Max. Min. Max. Min.Max. Max. Max. 19 214 12 330 35 10 0 1 0.7 6.6 20 214 16 320 25 10 0 10.7 6.6 21 214 16 325 25 2 10 0 1 0.7 6.6 22 214 16 330 20 2 10 0 1 0.76.6 23 214 16 330 25 4 10 0 1 0.7 6.6 24 214 20 310 15 2 8 0 1 0.7 6.625 214 20 310 20 4 8 0 1 0.7 6.6 26 214 20 305 25 6 8 0 1 0.7 6.6 27 21420 315 15 4 8 0 1 0.7 6.6 28 214 20 310 320 20 6 10 0 1 0.7 6.6 29 21420 295 320 10 4 10 0 1 0.7 6.6 30 214 20 295 325 10 6 10 0 1 0.7 6.6 31214 24 305 15 6 8 0 1 0.7 6.6 32 214 24 305 10 4 8 0 1 0.7 6.6 33 214 24310 10 6 8 0 1 0.7 6.6 34 214 28 295 10 4 6 0 1 0.7 6.6 35 214 28 295300 10 6 8 0 1 0.7 6.6 36 218 12 330 25 2 10 0 1 0.7 6.6 37 218 12 33030 4 10 0 1 0.7 6.6 38 218 16 320 20 8 10 0 1 0.7 6.6 39 218 16 320 15 610 0 1 0.7 6.6 40 218 16 320 10 4 10 0 1 0.7 6.6 41 218 16 325 15 8 10 01 0.7 6.6 42 218 16 325 10 6 10 0 1 0.7 6.6 43 218 16 330 10 8 10 0 10.7 6.6 44 218 20 310 5 8 10 0 1 0.7 6.6 45 214 12 295 320 35 8 1 2 0.76.6 46 214 12 295 320 25 8 10 1 2 0.7 6.6 47 214 12 320 330 35 10 1 20.7 6.6 48 214 16 295 325 35 8 1 2 0.7 6.6 49 214 16 325 330 25 2 10 1 20.7 6.6 50 214 20 295 315 25 2 8 1 2 0.7 6.6 51 214 20 320 20 2 8 1 20.7 6.6 52 214 20 325 15 4 8 1 2 0.7 6.6 53 214 20 330 10 6 8 1 2 0.76.6 54 214 24 305 25 2 6 1 2 0.7 6.6 55 214 24 310 15 2 8 1 2 0.7 6.6 56214 24 315 15 4 8 1 2 0.7 6.6 57 214 24 315 20 6 8 1 2 0.7 6.6 58 214 24320 15 6 8 1 2 0.7 6.6 59 214 28 300 25 2 6 1 2 0.7 6.6 60 214 28 305 254 6 1 2 0.7 6.6 61 214 28 310 15 4 6 1 2 0.7 6.6 62 214 28 310 10 2 6 12 0.7 6.6 63 214 28 315 5 2 6 1 2 0.7 6.6 64 218 12 325 35 8 1 2 0.7 6.665 218 12 330 25 10 1 2 0.7 6.6 66 218 12 310 330 30 2 10 1 2 0.7 6.6 67218 16 305 30 4 8 1 2 0.7 6.6 68 218 16 315 25 4 8 1 2 0.7 6.6 69 218 16320 15 2 8 1 2 0.7 6.6 70 218 16 325 15 4 8 1 2 0.7 6.6 71 218 16 315325 20 6 10 1 2 0.7 6.6 72 218 16 330 10 6 8 1 2 0.7 6.6 73 218 20 30515 4 8 1 2 0.7 6.6 74 218 20 305 20 6 8 1 2 0.7 6.6 75 218 20 310 10 4 81 2 0.7 6.6 76 218 20 310 5 2 8 1 2 0.7 6.6 77 218 20 315 5 4 8 1 2 0.76.6 78 218 20 320 5 6 10 1 2 0.7 6.6 79 218 24 295 5 4 8 1 2 0.7 6.6 80214 12 330 35 6 2 2.7 0.7 6.6 81 214 12 305 330 20 8 2 2.7 0.7 6.6 82214 16 315 35 6 2 2.7 0.7 6.6 83 214 16 320 30 6 2 2.7 0.7 6.6 84 214 16325 20 6 2 2.7 0.7 6.6 85 214 16 315 330 15 8 2 2.7 0.7 6.6 86 214 20320 30 4 2 2.7 0.7 6.6 87 214 20 305 320 30 6 2 2.7 0.7 6.6 88 214 20325 20 6 2 2.7 0.7 6.6 89 214 20 320 330 10 8 2 2.7 0.7 6.6 90 214 20330 15 4 6 2 2.7 0.7 6.6 91 214 24 310 35 4 2 2.7 0.7 6.6 92 214 24 31525 4 2 2.7 0.7 6.6 93 214 24 320 15 4 2 2.7 0.7 6.6 94 214 24 305 315 206 2 2.7 0.7 6.6 95 214 24 295 320 15 6 2 2.7 0.7 6.6 96 214 24 295 32510 4 6 2 2.7 0.7 6.6 97 214 28 305 35 4 2 2.7 0.7 6.6 98 214 28 310 30 42 2.7 0.7 6.6 99 214 28 305 315 10 6 2 2.7 0.7 6.6 100 214 28 305 320 102 6 2 2.7 0.7 6.6 101 218 12 330 35 6 2 2.7 0.7 6.6 102 218 12 305 33020 8 2 2.7 0.7 6.6 103 218 16 315 35 6 2 2.7 0.7 6.6 104 218 16 320 25 62 2.7 0.7 6.6 105 218 16 325 20 6 2 2.7 0.7 6.6 106 218 16 315 325 15 48 2 2.7 0.7 6.6 107 218 16 315 330 15 6 8 2 2.7 0.7 6.6 108 218 20 31020 6 2 2.7 0.7 6.6 109 218 20 315 15 6 2 2.7 0.7 6.6 110 218 24 300 20 42 2.7 0.7 6.6 111 218 24 305 15 6 2 2.7 0.7 6.6 112 218 24 310 10 6 22.7 0.7 6.6 113 218 28 300 20 4 2 2.7 0.7 6.6 114 218 28 305 10 4 2 2.70.7 6.6 115 218 28 315 5 4 6 2 2.7 0.7 6.6

The effect of changes in T₅₀ is shown in FIG. 1, with all otherproperties held at the flat limits set out above. FIG. 1 plots thepercentage change in emissions against values of T₅₀ (° F.).

This figure demonstrates the sensitivity of hydrocarbon emissions andtoxics to T₅₀ although NOx is insensitve to changes in this parameter.The addition of the RVP factor to the CARB Predictive Model (included inCARB emission inventory models) would, however, provide reductions inthe hydrocarbon evaporative levels which would increase the flexibilityto accommodate changes, both in increases in T₅₀ as well as in reducedoxygenate levels. Even a few tenths of one psi would, when factoroedappropriately into the model improve blending flexibility for pumpgasolines.

An alternative approach is to decrase T₅₀ below the 210° F. figure, asnoted for the third conforming fuel (above) within the existing CARBmodel which has the potential to use a higher value for T₉₀, includingpotential for extending gasoline end point and so increasing gasolinevolume production. This, in combination with other appropriatecompositional parameters as set out above, e.g., sulfur, olefins,aromatics, benzene, RVP, oxygen, E₂₀₀, E₃₀₀, values of T₅₀ in the range200 to 210° F. coupled with values of T₉₀ from 315 to 330° F., usually315 to 325° F., may be found useful from the viewpoint of giving greaterblend flexibility without increasing emissions above regulatory limits.Relatively higher values of T₅₀ may be encountered more frequently inthe higher octane grades, especially SUL (92-93 octane), associated withthe higher levels or aromatics in SUL, whereas RUL (87 octane) mayderive octane from the olefin content.

The use of T₉₀ values at the upper end of the permissible range is notrequired for emissions although it is desirable to increase the volumeof the gasoline pool. Lower values for T₉₀ can be used at the expense ofvolume, for example, T₉₀ from 280 to 300° F., e.g., from 290 to 300° F.

The effects of oxygenate content is shown in FIG. 2 which plots thepercentage change in emissions against the oxygen content (as oxygen),again with other fuel properties held at the flat limits set out above.

As shown in this figure, the hydrocarbon emissions decline withincreasing oxygenate levels although there is a slight increase in NOxand toxics over the range investigated. The levels of NOx and toxicsare, however, lower than those of the reference (flat limits) fuel up toan oxygenate content of 2.0 percent, within the CBG limits.

The provision of oxygenate is becoming problematical since there areconcerns about the spread of the most commonly used oxygenate, methyltert-butyl ether (MTBE) into the groundwater. Similar concerns arisealso with other ethers such as tert.-amyl methyl ether (TAME) and ethyltert-butyl ether (ETBE). It may therefore be desirable to usealternative sources of oxygen such as ethanol even though ethanol itselfgives rise to volatility problems and possibly other concerns, includingthe volumetric energy content, which is significantly lower than that ofthe base hydrocarbons. The use of ethanol in amounts up to about 3.5wt %(as oxygen) is allowed if appropriate other adjustments to compositionare made. Other oxygenates including alcohols such iso-propanol (IPA),as well as ethers such as di-iso-propyl ether (DIPE), MTBE, TAME, ETBEmay be used in accordance with the regulatory requirements in amounts upto 2.7 wt %, usually from 1.8 to 2.2 wt % (all oxygenates expressed aswt % oxygen).

The effect of olefins is shown graphically in FIG. 3, plottingpercentage change in emissions against olefin content, again with otherfuel properties at flat limits. Although, in this case, there is arelatively sharp increase in toxics emissions with increasing olefincontent, the level of toxics emissions at olefin levels up to about 6vol % remains below that of the flat limits reference gasoline. Thus,olefin levels up to about 6 vol % should be tolerable. Hydrocarbon andNOx emissions are inversely related with a smaller dependence on olefincontent. It is notable that the hydrocarbon emissions are greater atolefin levels up to about 6 vol % but if the RVP factor is included, itmay be possible to reduce overall HC emissions, as shown above. Olefinlevels up to the legally permitted values of 10 vol % (current legallimit) or even higher, for example, up to 15 vol % may not prove to beenvironmentally unacceptable. Since olefins tend to have a favorableeffect on octane, their inclusion in motor pump gasolines is desirablefrom the consumer's point of view as well as that of the refiner whotends to produce a large proportion of gasoline product by catalyticcracking, a process which results in relatively large quantities ofolefins, especially in the front end of the gasoline. Economically, theuse of olefins for octane in RUL is justified as compared to alkylate inthe more expensive higher octane grade SUL (92-93 octane). The use ofcatalytically cracked gasoline is also associated with the presence ofsignificant amounts of aromtics which again are desirable from theviewpoint of octane rating—aromatics are high octane components—as wellas from the view point of gas mileage, another environmental factor,since aromatics are high energy density components. The presence ofrelatively high aromatics levels is not inconsistent with good emissionsbehavior and for this reason, aromatics levels up to 25-35 vol % canreadily be accomodated in the gasolines.

Another factor requiring attention during the blending is DriveabilityIndex (DI). Driveability index is conventionally determined and statedaccording to ASTM D-86. According to this method, three distillationtemperatures, T₁₀, T₅₀, and T₉₀ are determined for a sample. Thedriveability index for the sample is then determined according to thefollowing equation:Driveability index=1.5(T₁₀)+3.0(T₅₀)+1(T₉₀)Since DI is relatively more dependent on T₅₀ than on T₁₀ and T₉₀,increases in T₅₀ as outlined above will tend to favor improvements inDI, which is desirable from the consumer's point of view. Representativevalues of DI for the gasolines set out here are in the range of 1100 to1200, more usually 1120 to 1185, for example, from 1135 to 1165.

1. An unleaded gasoline pump fuel which has the following properties:T₁₀, ° F. <=140 T₅₀, ° F. >215 = <220 T₉₀, ° F. <330 RVP, psi <=7.0 S,ppmw <=50 Oxygen, wt % <=3.5 Aromatics, vol % not more than 28 Olefins,vol % <=10 Benzene, vol % <=1.0 Paraffins, vol. pct. <=75 API° >=59.


2. The fuel according to claim 1 which has a RVP of 6.6 psi maximum. 3.The fuel according to claim 1 which has a RVP of 6.6 to 6.9 psi.
 4. Anunleaded gasoline pump fuel which possesses the following properties:T₁₀, ° F. <=140 T₅₀, ° F. >215 = <220 T₉₀, ° F. 315-330 S, ppmw <=35Oxygen, wt % <=2 Aromatics, vol % not more than 28 Olefins, vol % <=10Benzene, vol % <=1.0 Paraffins, vol % <=75 API° >=59 RVP, psi <=7.0.


5. The fuel according to claim 1 or 4 which has an octane rating of 92to 93 (R+M)/2 and an aromatics content of 12 to 20 vol percent and abenzene content of not more than 0.80 vol %.
 6. The fuel according toclaim 1 or 4 which has an octane rating of 87 (R+M)/2 and an aromaticscontent of 12 to 20 vol percent and a benzene content of not more than0.70 vol %.
 7. The fuel according to claim 1 or 4 which has a sulfurcontent of not more than 25 ppmw.